Elbow prosthesis

ABSTRACT

A prosthetic joint kit that is particularly well suited for an elbow. In each of the various embodiments, the prosthetic joint kit transmits load through the prosthetic joint through a pair of spherically shaped bearing surfaces so as to transmit load over a relatively large area rather than at a point or over a line of contact. The prosthetic joint kit may be configured in a modular manner wherein a plurality of interchangeable stem structures, being structures and/or bearing inserts of various types are available. Construction in this manner enables a surgeon to configure the prosthetic joint to best suit the needs of the patient. For example, the surgeon may employ a modular flange for compressing a bone graft, a tissue fastener for securing soft tissue to a portion of the prosthetic joint, a cam for limiting the amount by which the prosthetic joint articulates or a bearing insert for tailoring the degree of varus/valgus constraint.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/219,103 filed Jul. 18, 2000.

TECHNICAL FIELD

[0002] The present invention relates generally to prosthetic devicesused in elbow arthroplasty and more particularly to a modular elbowprosthesis.

BACKGROUND OF THE INVENTION BACKGROUND ART

[0003] Linked or constrained elbow prostheses are known which comprisesimple hinge arrangements, one component of which is attached to the endof the humerus and the other component of which is attached to the endof the ulna. The humeral component includes a shaft, that is cementedinto a prepared cavity in the end of the humerus, and the ulnarcomponent includes a shaft, that is cemented to the end of the ulna. Thecomponents of the prosthesis are connected together by means of a hingepin so that the prosthesis allows a single degree of freedom of movementof the ulna relative to the humerus.

[0004] One example of a linked elbow prostheses is disclosed in U.S.Pat. No. 6,027,534 to Wack et al. In several respects, the linkedembodiment of the '534 patent is typical of the designs for linked elbowprostheses in that it includes a humeral stem that terminates at a yokeat its distal end, a bearing component, a retaining pin and an ulnastem. The bearing component includes an oversized hole that is alignedwith the longitudinal axis of the bearing and adapted to accept theretaining pin in a slip-fit condition. The distal end of the bearingcomponent is coupled to the ulna stem. Despite the relatively widespreaduse of designs of this type, several drawbacks have been noted.

[0005] One significant drawback concerns the assembly of the elbowprosthesis after the surgeon has cemented the humeral and ulna stems totheir respective bones. In using such conventionally configured linkedelbow prosthesis devices, it is frequently necessary for the surgeon todrill a fairly large hole through the humerus so that the retaining pinmay be inserted to the yoke of the humeral stem and the humeral bearingcomponent. As a high degree of accuracy is typically required to ensureproper alignment between the hole in the humerus and the hole in theyoke of the humeral stem, a significant cost can be associated with thisstep in the installation of an elbow prosthesis due to the cost of thetooling used and the amount of time required to complete this step. Theother method for attaching the prosthetic device includes inserting thedevice in its linked condition or placing the remaining piece into theyoke prior to fully seating the humeral component into the bone. Thislater method is typically somewhat difficult, given the limited amountof joint space that is available and the time constraints associatedwith the use of a PMMA bone cement.

[0006] Unlinked, or unconstrained, elbow prostheses are known which aresimilar to linked elbow prostheses but do not have a specific componentwhich mechanically couples the humeral and ulnar stems together. Rather,the prosthetic device is held together by the patient's natural softtissues. One example of an unlinked elbow prostheses is also disclosedin U.S. Pat. No. 6,027,534 to Wack et al. In several respects, theunlinked embodiment of the '534 patent is similar to the linkedembodiment discussed above in that it includes a humeral stem thatterminates at a yoke at its distal end, a humeral bearing component, aretaining pin, an ulnar bearing component and a ulnar stem. The outersurface of the humeral bearing is contoured to match the contour of theulnar bearing component. Despite the relatively widespread use ofdesigns of this type, several drawbacks have been noted.

[0007] For instance, a retaining pin that is transverse to thelongitudinal axis of the patient is employed, thereby making its removaldifficult if a bearing need to be replaced.

SUMMARY OF THE INVENTION

[0008] It is a general object of the present invention to provide aprosthetic joint kit which transmits load through mating bearingcomponents over a spherically shaped area so as to minimize stresses inthe bearing components, more accurately mimic normal joint motion andprovide for ease of assembly and revision.

[0009] In one preferred form, the present invention provides aprosthetic joint kit having a first bearing component and a secondbearing component. The first bearing component includes a pair ofcondyle portions, each of which having a spherically shaped bearingportion. The second bearing component includes a pair of sphericalbearing portions which are configured to engage the spherically shapedbearing portions of the first bearing component.

[0010] It is another general object of the present invention to providea prosthetic joint kit having a high degree of modularity to permit asurgeon to easily configure the prosthetic joint kit to a patient.

[0011] In another preferred form, the present invention provides aprosthetic joint kit having a plurality of modular and interchangeablejoint components which permit a surgeon to easily configure theprosthetic joint kit to a patient. Modularity is achieved through aplurality of interchangeable components such as stem structures, bearingcomponents and bearing inserts.

[0012] It is yet another general object of the present invention toprovide a prosthetic joint kit having a plurality of interchangeablebearing inserts which permit a surgeon to tailor the degree ofvarus/valgus constraint in a desired manner.

[0013] In another preferred form, the present invention provides aprosthetic joint kit having a plurality of interchangeable bearinginserts, each of which having a pair of spherical depressions. Each ofthe spherical depressions has a first portion and a second portion, withthe second portion being formed in a manner that defines the degree ofvarus/valgus constraint.

[0014] It is a further object of the present invention to provide aprosthetic joint kit which effectively limits the amount by which theprosthetic joint will articulate.

[0015] In yet another preferred form, the present invention provides aprosthetic joint kit having a cam structure which is coupled to a firststem structure such that the first stem structure contacts a second stemwhen the first stem structure has been rotated to a predeterminedposition relative to the second stem structure.

[0016] It is yet another object of the present invention to provide aprosthetic joint kit which employs a spherically-shaped bearing surfaceto transmit load between stem structures yet does not require fastenersor other hardware to link the stem structures together.

[0017] In another preferred form, the present invention provides aprosthetic joint kit having a first stem structure with a retainingstructure and a first spherical bearing surface and a second stemstructure with a retaining aperture and a second spherical bearingsurface. The retaining aperture is configured to receive the retainingstructure when the first stem structure is at a first orientationrelative to the second stem structure. Relative rotation of the firststem structure from the first orientation causes retaining structure toengage a portion of the retaining aperture which precludes thewithdrawal of the retaining structure therefrom. The retaining apertureand retaining structure are sized so as not to transmit loadtherebetween, thereby ensuring that load is transmitted between thespherical bearing surfaces of the first and second stem structures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Additional advantages and features of the present invention willbecome apparent from the subsequent description and the appended claims,taken in conjunction with the accompanying drawings, wherein:

[0019]FIG. 1 is an exploded perspective view of a linked prostheticjoint kit constructed in accordance with the teachings of a first aspectof the present invention;

[0020]FIG. 1A is an exploded perspective view of a linked prostheticjoint kit similar to that of FIG. 1 but constructed in accordance with afirst alternate embodiment of the first aspect of the present invention;

[0021]FIG. 2 is a longitudinal cross-sectional view of the linkedprosthetic joint kit of FIG. 1 implanted in the arm of a person;

[0022]FIG. 3 is a cross-sectional view taken along the line 3-3 of FIG.2;

[0023]FIG. 4 is an exploded perspective view of an unlinked prostheticjoint kit constructed in accordance with the teachings of a first aspectof the present invention;

[0024]FIG. 5 is a longitudinal cross-sectional view of the unlinkedprosthetic joint kit of FIG. 4 implanted in the arm of a person;

[0025]FIG. 6 is an exploded plan view of a linked prosthetic joint kitconstructed in accordance with a second alternate embodiment of thefirst aspect of the present invention;

[0026]FIG. 7 is an enlarged portion of the linked prosthetic joint kitof FIG. 6;

[0027]FIG. 8 is an exploded plan view of a linked prosthetic joint kitconstructed in accordance with a third alternate embodiment of the firstaspect of the present invention;

[0028]FIG. 9 is a exploded side elevation view of a portion of a jointkit constructed in accordance with the teachings of a second aspect ofthe present invention;

[0029]FIG. 10 is an exploded side elevation view of a portion of a jointkit constructed in accordance with a first alternate embodiment of thesecond aspect of the present invention;

[0030]FIG. 11 is an exploded side elevation view of a portion of a jointkit constructed in accordance with a third alternate embodiment of thesecond aspect of the present invention;

[0031]FIG. 12 is a longitudinal cross-sectional view of a portion of ajoint kit constructed in accordance with a fourth alternate embodimentof the second aspect of the present invention;

[0032]FIG. 13 is an exploded side elevation view of a portion of a jointkit constructed in accordance with a fifth alternate embodiment of thesecond aspect of the present invention;

[0033]FIG. 14 is a cross-sectional view taken along the line 14-14 ofFIG. 13;

[0034]FIG. 15 is a cross-sectional view of a portion of a joint kitconstructed in accordance with a sixth alternate embodiment of thesecond aspect of the present invention;

[0035]FIG. 16 is an exploded side elevation view of a portion of linkedprosthetic joint kit constructed in accordance with the teachings of apreferred embodiment of a third aspect of the present invention;

[0036]FIG. 17 is a cross-sectional view taken along the line 17-17 ofFIG. 16;

[0037]FIG. 18 is a cross-sectional view taken along the line 18-18 ofFIG. 16;

[0038]FIGS. 19A through 19D are side elevation views of bearing insertsconstructed with varying degrees of varus/valgus constraint;

[0039]FIG. 20 is an exploded side elevation view of a portion of alinked prosthetic joint kit constructed in accordance with the teachingsof a first alternate embodiment of the third aspect of the presentinvention;

[0040]FIG. 20B is an exploded side elevation view of a portion of alinked prosthetic joint constructed in accordance with the teachings ofsecond alternate embodiment of the third aspect of the presentinvention;

[0041]FIG. 20C is a side view of an alternately constructed pin forlinking the stem structures of the second alternate embodiment of thethird aspect of the present invention;

[0042]FIG. 21 is a bottom plan view of a portion of the linkedprosthetic joint kit of FIG. 20 illustrating the bearing insert ingreater detail;

[0043]FIG. 22 is a side elevation view of a portion of the linkedprosthetic joint kit of FIG. 20 illustrating the clip member in greaterdetail;

[0044]FIG. 23 is a longitudinal cross-sectional view of a linkedprosthetic joint kit constructed in accordance with the teachings of apreferred embodiment of a fourth aspect of the present invention;

[0045]FIG. 24 is a top plan view of the linked prosthetic joint kit ofFIG. 23;

[0046]FIG. 25 is an exploded top plan view of a linked prosthetic jointkit constructed in accordance with the teachings of a preferredembodiment of a fifth aspect of the present invention;

[0047]FIG. 26 is a longitudinal cross-sectional view of the linkedprosthetic joint kit of FIG. 25;

[0048]FIG. 27 is a longitudinal cross-sectional view similar to that ofFIG. 2, but illustrating the stem with an integrally-formed flange forcompressing a bone graft;

[0049]FIG. 28 is a side view illustrating a stem with anintegrally-formed, resilient flange for compressing a bone graft;

[0050]FIG. 29 is a longitudinal cross-sectional view similar to that ofFIG. 2, but illustrating the stem of FIG. 28;

[0051]FIG. 30 is a longitudinal cross-sectional view similar to that ofFIG. 29, but illustrating the resilient flange as being fixedly butremovably coupled to the stem;

[0052]FIG. 31 is a partially broken-away exploded perspective viewillustrating an alternative coupling means for coupling the modularflange to the stem;

[0053]FIG. 32 is a longitudinal cross-sectional view similar to that ofFIG. 2, but illustrating the alternative coupling means of FIG. 31;

[0054]FIG. 33 is a view similar to that of FIG. 31 but illustrating asecond alternative coupling means;

[0055]FIG. 34 is a view similar to that of FIG. 31 but illustrating athird alternative coupling means;

[0056]FIG. 35 is a longitudinal cross-sectional view similar to that ofFIG. 2, but illustrating the alternative coupling means of FIG. 34.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0057] With reference to FIGS. 1, 2 and 3 of the drawings, a linkedprosthetic joint device constructed in accordance with the teachings ofa first aspect of the present invention is generally indicated byreference number 10. Although the particular prosthesis illustrated anddiscussed relates to a prosthesis for use in reconstructing an elbow, itwill be understood that the teachings of the present invention haveapplicability to other types of linked and unlinked prosthetic devices.As such, the scope of the present invention will not be limited toapplications involving elbow prosthesis but will extend to otherprosthetic applications.

[0058] In the particular embodiment illustrated, linked prosthetic joint10 is shown to include a first stem structure 12, a second stemstructure 14, a first bearing component 16, a second bearing component18, a modular flange 20 and a tissue fastener 22. First stem structure12 includes a proximal portion 30 and a distal portion 32. Proximalportion 30 includes a stem member 34 which is adapted to fit within themedullary canal 36 of a humerus 38. Distal portion 32 includes agenerally U-shaped member 40 which is fixedly coupled to the distal endof proximal portion 30. U-shaped portion 40 includes a pair ofspaced-apart legs or furcations 42. A threaded fastener aperture 44extends perpendicularly through each of the furcations 42.

[0059] Second stem structure 14 includes a distal portion 50 which isadapted to fit within the medullary canal 52 of an ulna 54. Second stemstructure 14 also includes a proximal portion 56 which is coupled tosecond bearing component 18. In the particular embodiment illustrated,second bearing component 18 is fixedly coupled to second stem structure14. However, second bearing component 18 may also be releasably coupledto second stem structure 14 as shown in FIGS. 9 through 12.

[0060] First bearing component 16 includes a pair of condyle portions60, a pin portion 62 and a pair of fasteners 64. Condyle portions 60 andpin portion 62 are formed from a suitable material, such as cobaltchromium alloy. Each condyle portion 60 is shown to include aspherically-shaped bearing portion 66, slotted aperture 68, a pinaperture 70 and a mounting aperture 72. The pair of spherically shapedbearing portions 66 collectively form a first bearing surface. Pinaperture 70 is sized to receive an end of pin portion 62 to permit pinportion 62 to slidingly engage condyle portions 60. Pin 62 can also befixedly coupled with one of said condyle portion 60 and slidingly engagesecond of said condyle portion 60. Each of the slotted apertures 68 issized to slidingly engage one of the furcations 42.

[0061] Second bearing component 18 is shown to include a cage portion 80which is fixedly coupled to the proximal portion 56 of second stemstructure 14 and a bearing member 82 which is fixedly coupled to thecage portion 80. Bearing member 82 includes a pair of spherical bearingportions 84 which are configured to engage the spherically shapedbearing portions 66 of the condyle portions 60. The pair of sphericalbearing surfaces 84 collectively form a second bearing surface thatmates with the first bearing surface. Bearing member 82 also includes athrough hole 86 which is adapted to receive pin portion 62, preferablywithout transmitting load therebetween (i.e., pin portion 62 preferablydoes not contact the surfaces of through hole 86). In the particularembodiment illustrated, bearing member 82 is fabricated frompolyethylene which has been molded to cage portion 80. Alternatively,bearing member 82 may be fabricated from any other appropriate materialsuch as a stainless steel, ceramic, pyrolytic carbon, cobolt chrome(CoCr) etc.

[0062] To use linked prosthetic joint 10, first stem structure 12 isimplanted in humerus 38 such that proximal portion 34 is located in themedullary canal 36 of the humerus 38 as shown in FIG. 2. Second stemstructure 14 is similarly implanted in ulna 54 such that distal portion50 is located in the medullary canal 52. Pin portion 62 is next insertedto the pin aperture 70 of one of the condyle portions 60 and theopposite end of pin portion 62 is placed through hole 86 and into thepin aperture 70 of the other one of the condyle portions 60. Secondbearing component 18 is positioned adjacent the distal portion 32 offirst stem structure 12, furcations 42 are aligned to their respectiveslotted aperture 68 and condyle portions 60 are slidingly engaged tofurcations 42. Fasteners 64 are inserted through their respectivemounting apertures 72 and threadably engaged to their threaded fasteneraperture 44. When fully seated, each of the fasteners 72, extendsthrough its respective furcation 42 to prevent condyle portion 60 fromrotating relative to the furcation 42. At this point, first and secondbearing components 16 and 18 hingedly couple first and second stemstructures 12 and 14 together in a linked or constrained manner.

[0063] Construction of linked prosthetic joint 10 in this manner ishighly advantageous in that it permits the surgeon to insert the firstand second stem structures 12 and 14 prior to or after assembling linkedprosthetic joint 10, as well as permits linked prosthetic joint 10 to beassembled in a relatively small space as compared to most of the otherprosthetic joints that are known in the art. Furthermore, the sphericalconfiguration of first and second bearing surfaces 66 and 84 permits theload which is transmitted through linked prosthetic joint 10 to bespread out over a relatively large area, rather than concentrated at asingle point or over a line of contact to thereby improve the durabilityof linked prosthetic joint 10.

[0064] Modular flange 20 may be employed to increase the resistance offirst stem structure 12 to rotation within medullary canal 36. In FIGS.1 and 2, modular flange 20 is shown to include an internally threadedfastener 90, and a unitarily formed flange structure 92 having a mountmember 94 and a flange member 96. Mount member 94 includes a locatingcylinder 94 a which is fixedly coupled to flange member 96 at its baseand an externally threaded fastener 94 b which is coupled to an oppositeside of locating cylinder 94 a. A mounting hole 98, which is sized toreceive fastener 94 b, extends through internally threaded fastener 90.A bore 100 formed through the base 102 of U-shaped portion 40 has afirst portion 104 which is tapered at one end to engage the edges ofinternally threaded fastener 90 and second portion 106 which is counterbored at the other end to engage the locating cylinder 94 a of mountmember 94. Internally threaded fastener 90 is threadably engaged tofastener 94 b to fixedly but removably couple modular flange 20 to firststem structure 12.

[0065] Modular flange 20 may be employed to generate a clamping forcewhich clamps a portion 108 of the humerus 38 between the proximalportion 34 of the first stem structure 12 and the flange member 96.Preferably, a bone graft 110 is employed in conjunction with modularflange 20 such that the clamping force produced by modular flange 20 isalso transmitted to bone graft 110 to promote the attachment of bonegraft 110 to humerus 38 and the subsequent growth of bone graft 110.Those skilled in the art will understand that alternatively, a flange(not shown) which is unitarily formed with first stem structure 12 maybe incorporated into linked prosthetic joint 10 to thereby increase theresistance of first stem structure 12 to rotation within medullary canal36. However, a flange which is unitarily formed with first stemstructure 12 could not be employed to generate a clamping force whichclamps a portion 108 of the humerus 38 between the proximal portion 34of the first stem structure 12 and the flange.

[0066] Tissue fastener 22 is shown in FIGS. 1 and 2 to be a device forattaching soft tissue, such as tendons 130, to linked prosthetic joint10. In this regard, the specific configuration of tissue fastener isbeyond the scope of this disclosure. Examples of suitable tissuefasteners are discussed in U.S. Pat. Nos. 5,380,334, 5,584,835,5,725,541, 5,840,078 and 5,980,557 which are hereby incorporated byreference as if fully set forth herein.

[0067] In the particular embodiment illustrated, tissue fastener 22 isshown to include a tissue clamp 132 and a threaded fastener 134. Tissueclamp 132 includes an annular base 136 and a pair of prongs 138. Prongs138 are forced through the soft tissue (e.g. tendons 130). Threadedfastener 134 is inserted through a hole in base 136 and threadablyengaged to second stem structure 14 to fixedly but releasably coupletissue fastener 22 and the soft tissue to second stem structure 14.Those skilled in the art will understand that tissue fastener 22 mayalso be used in conjunction with first stem structure 12.

[0068] In FIG. 1A, a linked prosthetic joint device constructed inaccordance with the teachings of an alternate embodiment of the firstaspect of the present invention is generally indicated by referencenumeral 10 a. Linked prosthetic joint 10 a is shown to include firststem structure 12, second stem structure 14, first bearing component 16a, second bearing component 18 a, modular flange 20 and tissue fastener22.

[0069] First bearing component 16 a is similar to first bearingcomponent 16 in all respects except that it is unitarily formed.Accordingly, pin portion 62 a is not removable form condyle portions 60a. Second bearing component 18 a is similar to second bearing component18 in all respects except that an insertion aperture 150 extends formthrough hole 86 a outwardly through bearing member 82 a and cage portion80 a. Accordingly, insertion aperture 150 renders the area of secondbearing surface 84 a somewhat smaller than second bearing surface 84.Second bearing surface 84 a is otherwise identical to second bearingsurface 84.

[0070] To use linked prosthetic joint device 10 a, first and second stemstructures 12 and 14 are initially inserted to the humerus and ulna andfirst bearing component 16 a is fastened to the first stem structure 12using techniques similar to that discussed above for prosthetic jointdevice 10. First bearing component 16 a is then positioned adjacentsecond bearing component 18 a such that pin portion 62 a is in insertionaperture 150. Pin portion 62 a is then forced toward through hole 86 a.The distal end 152 of insertion aperture 150 is smaller than pin portion62 a to permit bearing member 82 a to engage pin portion 62 a in a snapfit manner, so as to inhibit the unintentional withdrawal of pin portion62 a from through hole 86 a. As discussed above, through hole 86 a ispreferably larger in diameter than pin portion 62 a. At this point,first and second bearing components 16 a and 18 a hingedly couple firstand second stem structures 12 and 14 together in a linked manner.

[0071] In FIGS. 4 and 5, an unconstrained or unlinked prosthetic jointdevice constructed according to a first aspect of the present inventionis generally indicated by reference number 10′. Unlinked prostheticjoint 10′ is shown to include a first stem structure 12, a second stemstructure 14, a first bearing component 16′, a second bearing component18′, a modular flange 20 and a tissue fastener 22. Unlinked prostheticjoint 10′ is shown to be operatively associated with a humerus 38′ andan ulna 54′ (FIG. 5), but those skilled in the art will understand thatthe teachings of the present invention have application to prostheticjoints for other applications and as such, the scope of the presentinvention will not be limited to elbow joints.

[0072] First bearing component 16′ is similar to first bearing component16 in that it includes a pair of condyle portions 60′ and a pin portion62′. However, first bearing component 16′ is preferably unitarily formedwith pin portion 62′ extending between the spherically-shaped bearingportions 66′ and fixedly coupling the spherically-shaped bearingportions 66′ thereto. Like first bearing component 16, each of thecondyle portions 60′ of first bearing component 16′ includes a slottedaperture 68 and a fastener aperture 72. Spherically shaped bearingportions 66′ collectively form a first bearing surface. Like firstbearing component 16, first bearing component 16′ may be made from anyappropriate bearing material, such as cobalt chromium alloy.

[0073] Second bearing component 18′ is similar to second bearingcomponent 18 in that it includes a cage portion 80′ which is fixedlycoupled to the proximal portion 56 of second stem structure 14 and abearing member 82′ which is fixedly coupled to the cage portion 80′. Forpurposes of clarity, bearing member 82′ has not been shown in crosssection in FIG. 5. Bearing member 82′ includes spherical bearingsurfaces 84′ which are adapted to engage the spherically-shaped bearingportions 66′ of the condyle portions 60′. The pair of bearing surfaces84′ collectively form a second bearing surface that mates with the firstbearing surface. Bearing member 82′ also includes a raised portion 160which is adjacent the spherical bearing surfaces 84′ and configured toclear pin portion 62′, preferably without transmitting load therebetween(i.e., pin portion 62′ preferably does not contact the surfaces ofraised portion 160). In the particular embodiment illustrated, bearingmember 82′ is fabricated from polyethylene which has been molded to cageportion 80. Alternatively, bearing member 82′ may be fabricated from anyother appropriate material such as a cobalt chromium alloy, ceramics orstainless steel.

[0074] To use unlinked prosthetic joint 10′, first stem structure 12 isimplanted in humerus 38′ such that proximal portion 34 is located in themedullary canal 36′ as shown in FIG. 5. Second stem structure 14 issimilarly implanted in ulna 54′ such that distal portion 50 is locatedin the medullary canal 52′. First bearing component 16′ is nextpositioned adjacent the distal portion 32 of first stem structure 12 andfurcations 42 are engaged to slotted apertures 68. Fasteners 64 areinserted through their respective mounting apertures 72 and threadablyengaged to their threaded fastener aperture 44. When fully seated, eachof the fasteners 64, extends through its respective furcation 42 toprevent its associated condyle portion 60′ from rotating relative tothereto. The proximal end of the ulna 54′ is positioned adjacent thedistal end of the humerus 38′ such that the pin portion 62′ is proximatethe raised portion 160 and the spherically-shaped bearing portions 66′of the condyle portions 60′ engage the spherical bearing surface 84′. Atthis point, first and second bearing components 16′ and 18′ are coupledtogether in an unconstrained or unlinked manner (i.e., held in positionby the soft tissues of the elbow). Construction of unlinked prostheticjoint 10′ in this manner provides many of the same advantages asmentioned above for linked prosthetic joint 10, such as the ability offirst and second bearing surfaces 16′ and 18′ to spread out the loadthat is transmitted through unlinked prosthetic joint 10′ over arelatively large area, rather than concentrate the load at a singlepoint or over a line of contact to thereby improve the durability ofunlinked prosthetic joint 10′.

[0075] As a surgeon may not always know prior to beginning an operationwhether a patient would be better served by a linked or an unlinkedjoint prosthesis and as it is also occasionally necessary to convert anunlinked joint prosthesis to a constrained joint prosthesis, or viceversa, after implementation and use for a period of time, it is highlydesirable that the joint prosthesis be modular so as to provide thesurgeon with a high degree of flexibility which may be achieved in arelatively simple and cost-effective manner.

[0076] In FIGS. 6 and 7, a linked prosthetic joint constructed inaccordance with a second aspect of the present invention is generallyindicated by reference numeral 10 b. Linked prosthetic joint 10 b isshown to include first stem structure 12, a third stem structure 180,first bearing component 16, a third bearing component 182. Third stemstructure 180 is similar to second stem structure 14 in that it includesa distal portion 184 which is adapted to fit within the medullary canalof an ulna. The proximal portion 186 of third stem structure 180 iscoupled to third bearing component 182.

[0077] Third bearing component 182 is similar to second bearingcomponent 18 in that it includes a cage portion 190 and a bearing member192. Cage portion 190 is fixedly coupled to the proximal portion 186 ofthird stem structure 180. Bearing member 192 is fixedly coupled to cageportion 190. Bearing member 192 includes a pair of spherical bearingsurfaces 194 which are configured to engage the spherically-shapedbearing portions 66 of the condyle portions 60 and a through hole 196which is configured to receive pin portion 62, preferably withouttransmitting load therebetween (i.e., pin portion 62 preferably does notcontact the surfaces of through hole 196). Bearing member 182 alsoincludes a lateral buttress 200. Lateral buttress 200 includes asupplementary bearing surface 201 which is configured for receiving acapitellum 202 of the humerus 204. In the particular embodimentillustrated, third bearing component 182 is fixedly coupled to thirdstem structure 180 and as such, the combination of the second stemstructure 14 and second bearing component 18 is interchangeable with thecombination of the third stem structure 180 and the third bearingcomponent 182. However, those skilled in the art will understand thatsecond and third bearing components 18 and 182 may also be releasablycoupled to a stem structure, thereby eliminating the need for a thirdstem structure 180 which would otherwise be identical to second stemstructure 14. Those skilled in the art will also understand that thelateral butress may alternatively be coupled directly to the third stemstructure 180, being either releasably attached thereto or integrallyformed therewith.

[0078] In FIG. 8, another linked prosthetic joint constructed inaccordance with the teachings of a second aspect of the presentinvention is generally indicated by reference numeral 10 c. Linkedprosthetic joint 10 c is shown to include first stem structure 12,second stem structure 14, a fourth stem structure 220, second bearingcomponent 18, a fourth bearing component 222 and a fifth bearingcomponent 224. Fourth stem structure 220 includes a distal end 226 whichis adapted to fit within the medullary canal of a radius and a proximalend 228 which is fixedly coupled to fourth bearing component 222. Fourthbearing component 222 includes a fourth bearing surface 230.

[0079] Fifth bearing component 224 is similar to first bearing component16 in that it includes, for example, a pair of condyle portions 60 and apin portion 62 which permits first and fifth bearing components 16 and224 to be interchangeable. However, fifth bearing component 224 alsoincludes a lateral extension 240 which is adapted to replace at least aportion of the capitellum of the humerus. Lateral extension 240 definesa fifth bearing surface 242 which is configured to mate with fourthbearing surface 230. Preferably, at least a portion of each of thefourth and fifth bearing surfaces 230 and 242 is spherically shaped topermit loads transmitted therebetween to be spread out over a relativelylarge area, rather than be concentrated at a single point or along aline of contact.

[0080] In FIG. 9, a portion of a modular prosthetic joint kitconstructed in accordance with the teachings of a second aspect of thepresent invention is generally indicated by reference numeral 10 d.Modular prosthetic joint kit 10 d is shown to include second stemstructure 14 d, second bearing component 18 d, second bearing component18 e and a fastener 250.

[0081] Second bearing components 18 d and 18 e are similar to secondbearing components 18 and 18′, respectively, but are shown to beseparable from second stem structure 14 d. Second bearing components 18d and 18 e also include a keel member 252, a clip member 254 and afastener aperture 256 which are formed in cage portions 80 d and 80 e,respectively. Keel member 252 extends circumferentially around at leasta portion of the perimeter of each of the cage portions 80 d and 80 ebetween clip member 254 and fastener aperture 256. Clip member 254includes a first portion 258 which extends generally perpendicularlyoutward from its associated cage portion and a second portion 260 whichis coupled to the distal end of first portion 258. Second portion 260extends generally outwardly and away from first portion 258. Fasteneraperture 256 is located across from clip member 254 and is sized toreceive fastener 250.

[0082] Second stem structure 14 d is similar to second stem structure 14in that it includes a distal end 50 which is adapted to fit within themedullary canal of an ulna. Second stem structure 14 d also includes aproximal portion 56 d having a keel slot 264, a hook structure 266 andan internally threaded fastener aperture 268. Keel slot 264 is a slotthat is sized to receive keel member 252 in a slip fit manner. Keel slot264 and keel member 252 cooperate to resist relative medial-lateralmotion of cage portion (e.g. 80 d) relative to second stem structure 14d. Hook member 266 is generally U-shaped and defines a clip aperture 270which is sized to receive clip member 254.

[0083] To use modular prosthetic joint kit 10 d, the distal end 50 ofsecond stem structure 14 d is inserted in the medullary canal of theulna. The modularity of the prosthetic joint kit 10 d permits thesurgeon to assess the patient's elbow to determine if the patient wouldbe better served by a linked or an unlinked joint prosthesis. Once adecision has been made as to which type of joint prosthesis would betterserve the patient, the surgeon selects an appropriate one of the secondbearing components 18 d and 18 e, places its clip member 254 into theclip aperture 270, pivots the cage portion (i.e. 80 d) toward theproximal end 56 d of the second stem structure 14 d to engage the keelmember 252 into the keel slot 264, inserts the fastener 250 through thefastener aperture 256 and threadably engages the fastener 250 to theinternally threaded fastener aperture 268 to fixedly but releasablycouple the second stem structure 14 d with the selected one of thesecond bearing components 18 d and 18 e.

[0084] Those skilled in the art will understand that second bearingcomponents 18 d and 18 e may be coupled to second stem structure 14 d invarious other manners as illustrated in FIGS. 10 through 15. In FIG. 10,second bearing component 18 f is shown to include a generally L-shapedtray portion 280 which is fixedly coupled to cage portion 80 f. Trayportion 280 includes a keel slot 282 and a fastener aperture 284. Keelslot 282 is operable for receiving a keel member 286 formed into theproximal end 56 f of second stem structure 14 f. Fastener aperture 284is operable for receiving a fastener 288 which may be threadably engagedto an internally-threaded fastener aperture 290 in the proximal end 56 fof second stem structure 14 f to thereby permit second bearing component18 f and second stem structure 14 f to be fixedly but releasablycoupled.

[0085] When coupled together, keel slot 282 and keel member 286cooperate to resist relative medial-lateral motion of cage portion 80 frelative to second stem structure 14 f. Additionally, tray portion 280cooperates with an L-shaped flange 292 to which it abuts to furtherresist relative rotation between second stem structure 14 f and cageportion 80 f.

[0086] In FIG. 11, second bearing components 18 g and 18 h are shown toinclude a stem member 300 which extends from their respective cageportions 80 g and 80 h. Stem member 300 is engagable with a stemaperture 302 formed into the proximal end 56 g of second stem structure14 g. As shown in FIG. 12, stem member 300′ may alternatively beincorporated into the proximal end 56 j of second stem structure 14 jand stem aperture 302′ may be formed into cage portion 80 j of secondbearing component 18 j.

[0087] To provide the surgeon with additional flexibility, secondbearing component 18 h is shown in FIG. 11 to be slightly longer thansecond bearing component 18 g (i.e. the distances from the centerline ofbearing member 82 to the confronting surface 304 of their respectivecage portions 80 g and 80 h is shorter for second bearing component 18g). This variation between second bearing components 18 g and 18 hpermits the surgeon to adjust the length of prosthesis 10 g to take intoaccount the physical characteristics of the patient's arm.

[0088] Modularity may also be incorporated into first stem structure 12k as shown in FIGS. 13 and 14. First stem structure 12 k is shown toinclude a stem member 320 and a yoke member 322. The proximal end 324 ofstem member 320 is adapted to fit within the medullary canal of ahumerus and the distal end 326 of stem member 320 terminates at adovetail aperture 328 having a pair of inwardly tapering walls 330 and atapered retaining wedge 332. An internally threaded fastener aperture334 extends through retaining wedge 332. Yoke member 322 is shown to besimilar to the distal end 32 of first stem structure 12 as it includesfurcations 42 and threaded fastener apertures 44. Yoke member 322 alsoincludes a dovetail member 338 having a pair of outwardly taperingsurfaces 340, a wedge slot 342 and a through hole 344. Dovetail member338 is configured to mate with dovetail aperture 328 such thatengagement of retaining wedge 332 to the upper surface 346 of wedge slot342 forces tapered surfaces 340 against a respective one of the inwardlytapering walls 330. A fastener 350 is inserted through hole 344 andthreadably engaged to internally threaded fastener aperture 334 tofixedly but releasably couple yoke member 322 and stem member 320together.

[0089] Referring back to FIG. 11, second bearing components 18 g and 18h are also shown to include a pair of tang members 360. Each of the tangmembers 360 extends outwardly from its respective cage portion (i.e., 80g) and in the particular embodiment illustrated, is generallyrectangularly shaped. Each of the tang members 360 is sized to engage atang recess 362 in the proximal end 56 g of the second stem structure 14g. Engagement of the tang members 360 into their respective tang recess362 inhibits relative rotation between the second stem structure 14 gand the second bearing components 18 g and 18 h.

[0090] In FIG. 15, second bearing component 18 m is shown to have afastener aperture 380 which is formed through a bearing member 82 m andcage portion 80 m. Second stem structure 14 m, which is a threadedfastener 382 in this embodiment, is disposed through the fasteneraperture 380 in second bearing component 18 m and threadably engaged tothe cancellous bone 384 of the ulna 54 m. Construction in this manner isadvantageous in that it permits the extent of the trauma experienced bythe patient to be minimized. To further this goal, the distal end 386 ofcage portion 80 m is shown to be generally cylindrically shaped so as tominimize the amount of bone that must be removed to prepare the ulna 54m for the second bearing component 18 m.

[0091] In FIGS. 16 through 18, a portion of a modular prosthetic jointkit constructed in accordance with the teachings of a third aspect ofthe present invention is generally indicated by reference numeral 10 n.Modular prosthetic joint kit 10 n is shown to include a bearing insert400, a retaining ring 402 and a second stem structure 14 n having anintegrally attached cage portion 80 n. Cage portion 80 n is shown toinclude a bearing aperture 406 for receiving bearing insert 400. In theparticular embodiment illustrated, cage portion 80 n also includes acircumferentially extending first ring groove 408 formed along theperimeter of bearing aperture 406 and operable for receiving a firstportion of retaining ring 402.

[0092] Bearing insert 400 is generally cylindrically shaped, having apair of spherical depressions 420 which collectively form a bearingsurface that is configured to mate with the spherically-shaped bearingportions 66 of the first bearing component 16. Bearing insert 400 alsoincludes a through hole 422 which is adapted to receive pin portion 62,preferably without transmitting load therebetween. A circumferentiallyextending second ring groove 424 is formed in the outer perimeter ofbearing insert 400, the second ring groove 424 being operable forreceiving a second portion of retaining ring 402. Construction in thismanner is advantageous in that the surgeon may select a bearing insert400 from a plurality of bearing inserts 400 to adapt prosthetic joint 10n to the patient.

[0093] In the particular embodiment illustrated, bearing aperture 406 isshown to include a plurality of radially outwardly extending tabapertures 430 and bearing insert 400 is shown to include a plurality ofradially outwardly extending tabs 432. If desired, a first one of thetab apertures 430 and a first one of the tabs 432 may be sizeddifferently than the remaining tab apertures 430 and tabs 432,respectively, to key the bearing insert 400 to a specific orientationrelative to second stem structure 14 n.

[0094] With specific reference to FIG. 18, each of the pair of sphericaldepressions 420 includes a first spherical portion 450 and a secondspherical portion 454. Each of the first spherical portions 450 areformed into bearing insert 400 along an axis 456 that is coincident withthe longitudinal centerline of the bearing insert 400. Each of the firstspherical portions 450 are formed by a spherical radius approximatelyequal in magnitude to the spherical radius which defines thespherically-shaped bearing portion 66 of each of the condyle portions 60of first bearing component 16. The distance between the spherical radiialong axis 456 is equal to a predetermined distance, d.

[0095] The centerpoint 456 of the spherical radius that defines one ofthe first spherical portions 450 is employed to generate the secondspherical portion 454 on the opposite face of the bearing surface. Asecond centerline 468 is constructed from centerpoint 460 toward theopposite face at a predetermined constraint angle 470, such as 3.5degrees. The spherical radius that defines the second spherical portion454 on the opposite face is generated from a second centerpoint 472which is positioned along the second centerline 468 at a distance d fromcenterpoint 460. Construction of bearing insert 400 in this mannerpermits first bearing component 16 to rotate about centerline 456, aswell as to pivot relative to bearing insert 400 about thespherically-shaped bearing portion 66 of each of the condyle portions60.

[0096] A transition zone 480 is formed between each of the first andsecond spherical portions 450 and 454 wherein a radius is formed at theintersection of the radii which define the first and second sphericalportions 450 and 454 to “soften” the transition between the first andsecond spherical portions 450 and 454 to render the movement of thecondyle portions 60 over the first and second spherical portions 450 and454 more comfortable to the patient.

[0097] Those skilled in the art will understand that the degree of theconstraint may be defined by the constraint angle. Accordingly, modularprosthetic joint kit 10 n preferably includes a plurality of bearinginserts 400, each having a bearing surface with a second sphericalportion 454 that is defined by a different constraint angle. Thoseskilled in the art will also understand that the degree of theconstraint may be additionally or alternatively defined by a constraintcharacteristic, which is illustrated in FIGS. 19A through 19D.

[0098] In FIG. 19A, bearing insert 400 a has a first predeterminedconstraint characteristic orientation wherein the centerlines whichdefine the radii which define first and second spherical portions 450and 454 are contained in a plane which is generally perpendicular to thelongitudinal axis of the ulna. Construction of bearing insert 400 a inthis manner provides a varying degree of axial constraint. In FIG. 19B,bearing insert 400 b has a second predetermined constraintcharacteristic wherein the centerlines which define the radii whichdefine first and second spherical portions 450 and 454 are contained ina plane which is at approximately 45° to the longitudinal axis of theulna. Construction of bearing insert 400 b in this manner provides avarying degree of a combination of axial and varus/valgus constraint. InFIG. 19C, bearing insert 400 c has a third predetermined constraintcharacteristic wherein the centerlines which define the radii whichdefine first and second spherical portions 450 and 454 are contained ina plane which is generally parallel the longitudinal axis of the ulna.Construction of bearing insert 400 c in this manner provides a varyingdegree of varus/valgus constraint. In FIG. 19D, bearing insert 400 d isconstructed in a manner that is generally similar to that of bearinginserts 400 a, 400 b and 400 c except that the constraint angle employedto construct bearing insert 400 d is rotated form point x¹ to y¹ asindicated in FIG. 19d. As a result, there is no single line oforientation in which the constraint is limited. Construction of bearinginsert 400 d in this manner provides a varying degree of constraint inboth an axial direction and a varus/valgus direction.

[0099] In FIGS. 20 through 22, a portion of a modular prosthetic jointkit constructed in accordance with the teachings of an alternateembodiment of the third aspect of the present invention is generallyindicated by reference numeral 10 p. Modular prosthetic joint kit 10 pis similar to modular prosthetic joint kit 10 n in that it includes abearing insert 400 p and a second stem structure 14 p having aintegrally attached cage portion 80 p.

[0100] Cage portion 80 p is shown to include a bearing aperture 406 pfor receiving bearing insert 400 p. In the particular embodimentillustrated, cage portion 80 p includes a plurality of tab apertures 430p, a plurality of tab slots 500 and a hook structure 502. Each of thetab apertures 430 p extends axially through cage portion 80 p andcircumferentially around a portion of bearing aperture 406 p. Each ofthe tab slots 500 intersects one of the tab apertures 430 p and extendscircumferentially around a portion of bearing aperture 406 p away fromits associated tab aperture 430 p. Hook structure 502 is adjacent one ofthe tab apertures 430 p and extends radially inwardly andcircumferentially around a portion of bearing aperture 406 p. A clipslot 510 is formed circumferentially through hook structure 502.

[0101] Bearing insert 400 p is generally similar to bearing insert 400except for the configuration of the plurality of tabs 432 p and theincorporation of a clip structure 520 into a bearing body 522. Each ofthe plurality of tabs 432 p is relatively thin and do not extend axiallyacross bearing insert 400 p. This permits the tabs 432 p of bearinginsert 400 p to be aligned to a tab aperture 430 p and bearing insert400 p to be rotated so that each of the tabs 432 p is disposed withinone of the tab slots 500 to thereby prevent bearing insert 400 p frommoving in an axial direction.

[0102] Clip structure 520 is preferably a metal or plastic fabricationwhich is suitable for molding into bearing body 522. Clip structure 520includes an arm structure 530 which extends from a clip body 532 andterminates at its distal end at a hook member 534. Clip structure 520 isconfigured and incorporated into bearing body 522 such when bearinginsert 400 p is rotated to engage tabs 432 p into tab slots 500, armstructure 530 simultaneously engages clip slot 510 in hook structure502. Rotation of bearing insert 400 p to a predetermined rotationalposition relative to hook structure 502 permits hook member 534 toengage an edge 540 of hook structure 502. Arm structure 530 resilientlybiases hook member 534 against edge 540, thereby inhibiting rotation ofbearing insert 400 p which would cause tabs 432 p to disengage tab slots500.

[0103] In FIG. 20B, bearing insert 400 p′ is illustrated to beconfigured similarly to bearing insert 400 p except that a lockingaperture 800 is formed into one of the tabs 432 p′. Bearing insert 400p′ is inserted into bearing aperture 406 p′ aligned such that each ofthe tabs 432 p′ is aligned to an associated one of the tab apertures 430p′. Bearing insert 400 p′ is then rotated so that each of the tabs 500′is disposed within one of the tab slots 440 p′ and locking aperture 800is aligned to a corresponding locking aperture 802 formed in theintegrally attached cage portion 80 p′ of second stem structure 14 p′.Engagement of tabs 500′ into their respective tab slots 440 p′ preventsbearing insert 400 p′ from moving in an axial direction. Alignment oflocking apertures 800 and 802 to one another permits a pin 806 to beinserted therethrough to prevent bearing insert 400 p′ from rotatingrelative to integrally attached cage portion 80 p′. In the particularembodiment illustrated, pin 806 includes a head portion 808, a bodyportion 810 and an end portion 812. Head portion 808 has a diameterwhich is larger than the diameter of the hole formed by lockingapertures 800 and 802. Body portion 810 is preferably smaller indiameter than the diameter of the hole formed by locking apertures 800and 802.

[0104] A plurality of slots 814 are formed in end portion 812 whichcreates a plurality of fingers 816 which are flexible relative to thelongitudinal axis of pin 806. Fingers 816 flex inwardly toward thelongitudinal axis of pin 806 when pin 806 is inserted to lockingapertures 800 and 802, eliminating the interference therebetween topermit the fingers 816 of end portion 812 to pass through integrallyattached cage portion 80 p′ and bearing insert 400 p′. Once the fingers816 have passed through integrally attached cage portion 80 p′ andbearing insert 400 p′, they flex outwardly away from the longitudinalaxis of pin 806 to inhibit the unintended withdrawal of pin 806 fromlocking apertures 800 and 802. Intended withdrawal of pin 806 fromlocking apertures 800 and 802 may be effected through the flexing offingers 816 inwardly toward the longitudinal axis of pin 806.

[0105] Those skilled in the art will understand, however, that the pin806 for linking first and second stem structures 12 and 14 p′ may beconstructed differently. As shown in FIG. 20C, for example, the pin 806′includes head and end portions 808′ and 812′ having chamfered abuttingsurfaces 808 p′ and 812 p′, respectively. Additionally, the end portion812′ includes a chamfered lead portion 812 p″. Pin 806′ is installed bysimply pressing it through the bearing insert 400 p′.

[0106] In FIGS. 23 and 24, a portion of a modular prosthetic joint kitconstructed in accordance with the teachings of a fourth aspect of thepresent invention is generally indicated by reference numeral 10 q.Prosthetic joint kit 10 q is shown to include first stem structure 12,second stem structure 14, first bearing component 16 and second bearingcomponent 18 q. Second bearing component 18 q is substantially similarto second bearing component 18 except that cage portion 80 q is shown toinclude a cam structure 600. Cam structure 600 includes a lobe member602 that extends radially outwardly and terminates at a tip 604. Lobemember 602 is configured such that tip 604 contacts the base 102 ofU-shaped member 40 to inhibit further relative rotation between firstand second stem structures 12 and 14 when the first and second stemstructures 12 and 14 are placed in a position corresponding to themaximum extension of a patient's arm. Configuration of second bearingcomponent 18 q in this manner is advantageous in that it limits theamount by which a patient may rotate their ulna relative to theirhumerus to prevent hyperextension of the joint.

[0107] In FIGS. 25 and 26, a portion of a modular prosthetic joint kitconstructed in accordance with the teachings of a fifth aspect of thepresent invention is generally indicated by reference numeral 700.Prosthetic joint kit 700 is shown to include a first stem structure 702and a second stem structure 704. First stem structure 702 includes astem member 710, the distal end of which is configured to fit within themedullary canal of an ulna. A first bearing 712 and a coupling structure714 are incorporated into the proximal end of first stem structure 702.First bearing structure 712 is generally spherically shaped. Couplingstructure 714 includes a link member 720 and a retainer member 722. Linkmember 720 is fixedly coupled to first bearing 712 at a first end and toretaining structure 722 at a second end with link member 720 extendingtherebetween along an axis generally coincident the longitudinal axis offirst stem structure 702. Retaining structure 722 is illustrated to bespherically shaped with flattened ends.

[0108] Second stem structure 704 is shown to include a stem member 730with a proximal end that is configured to fit within the medullary canalof a humerus. A second bearing structure 732 is incorporated into thedistal end of second stem structure 704. Second bearing structure 732includes a generally spherical second bearing surface 740 and a T-shapedcoupling aperture 742. A first portion 744 of coupling aperture 742 hasa width which is larger than the width of retaining structure 722. Firstportion 744 is oriented at a position of maximum flexion. In theparticular embodiment illustrated, the position of maximum flexion isillustrated to be about 90° to the longitudinal axis of second stemstructure 704. However, those skilled in the art will understand thatthe position of maximum flexion may be tailored in a desired manner andmay range as high to an angle of approximately 135° to 150° to thelongitudinal axis of second stem structure 704, depending on theparticular application. A second portion 746 of coupling aperture 742has a width which is slightly larger than that of link member 720.Second portion 746 extends circumferentially around a portion of secondbearing surface 740 in a plane that coincides with the longitudinal axisof second stem structure 704. The first and second portions 744 and 746of coupling aperture 742 intersect and terminate at spherically shapedcavity 750.

[0109] To use prosthetic joint kit 700, first and second stem structures702 and 704 are inserted into the medullary canals of the ulna andhumerus, respectively. First stem structure 702 is then positionedproximate the first portion 744 of coupling aperture 742 and retainingstructure 722 is inserted through first portion 744 and into sphericallyshaped cavity 750. At this point, first and second bearing surfaces 712and 740 are in contact with one another and transmit load therebetweenrather than through coupling structure 714. Coupling of first and secondstem structures 702 and 704 is complete when first stem structure 702 isrotated into second portion 746. In this position, first and second stemstructures 702 and 704 are linked or constrained since the width ofretaining portion 722 is larger than the width of second portion 746 andthereby prevents the withdrawal of first stem structure 702 fromcoupling aperture 742.

[0110] While the prosthetic joint devices 10 and 10 a have beenillustrated as having modular flanges 20 that are fixedly but removablycoupled to the first stem structure 12, those skilled in the art willunderstand that the invention, in its broader aspects, may beconstructed somewhat differently. For example, the stem structure andmodular flange may be unitarily formed as shown in FIG. 27. In thisembodiment, the stem 12 p is illustrated to be similar to the stem 12,but includes a flange structure 92 p having a flange member 96 p and acoupling portion 96 p′ that couples the flange member 96 p to the distalportion 32 p of the stem 12 p. The flange member 96 p is generallyparallel the stem member 30 p and is employed to compress a bone graftagainst the stem member 30 p. Unlike the modular flange 20 that wasdescribed in detail, above, the flange structure 92p must be fitted overa bone graft 110 or the bone graft must be placed into the aperture 800between the stem member 30 p.

[0111] Another example of an integrally formed (i.e., non-removable)flange structure is illustrated in FIGS. 28 and 29. In this example, thestem 12 q is illustrated to be similar to the stem 12 p in that itincludes a flange structure 92 q having a flange member 96 q and acoupling portion 96 q′ that couples the flange member 96 q to the distalportion 32 q of the stem 12 q. The flange member 96 q, however, isarcuately shaped and includes a contact tab 804. The flange structure 92q is formed with a predetermined degree of resiliency, which may resultfrom the characteristics of the material from which the flange structure92 q is formed or by controlling the geometry (i.e., cross-sectionalshape and area) of the flange structure 92 q. The resiliency of theflange structure 92 q permits the flange member 96 q to act as a leafspring that biases the contact tab 804 toward the stem member 30 q.Accordingly, the flange may be employed to apply compression to the bonegraft 110 q without fasteners or other securing means. As illustrated inFIG. 30, those skilled in the art will readily understand, however, thata predetermined amount of resiliency may also be incorporated into aflange structure 92 r that is fixedly but removably coupled to the stem12 r.

[0112] Those skilled in the art will also understand that although themodular flange 20 has been illustrated as being coupled to the stem 12 rvia a threaded fastener 94 b, the invention, in its broader aspects, maybe constructed somewhat differently. For example, cables 810 areemployed to fixedly but removably retain the flange structure 92 s tothe stem 12 s as illustrated in FIGS. 31 and 32. The stem 12 s isgenerally similar to the stem 12, but includes a first coupling feature812 instead of the bore 100. The flange structure 92 s includes a flangemember 96 s and a coupling portion 96 s′. The coupling portion 96 s′includes a second coupling feature 814 that is configured to cooperatewith the first coupling feature 812 to locate the flange member 96 srelative to the distal portion 32 s of the stem 12 s. In the exampleillustrated, the first coupling feature 812 is a generally trapezoidaldovetail member 816 that extends outwardly from the distal portion 32 sof the stem 12 s and the second coupling feature 814 is a dovetailaperture 818 that is formed into the coupling portion 96 s′ and sized toengage the dovetail member 816 in with a line-to-line fit (i.e., withvery little or no clearance). The dovetail member 816 is preferablyintegrally formed onto the stem 12 s but may alternatively be anindependently formed component that is fixedly coupled to the distalportion 32 s via an appropriate coupling means, such as threadedfasteners, press-fitting or shrink fitting.

[0113] The flange member 96 s is shown to include a plurality ofcross-holes 820 that extend completely through the flange member 96 s ina direction that is generally perpendicular the longitudinal axis of theflange member 96 s. The cross-holes 820 are sized to receive the cable810. As those skilled in the art will understand, the cables 810 arefirst secured around the humerus 38 s and the ends of the cables 810 areloosely secured via an appropriate coupling device, such as a cablesleeve 822. The cables 810 are then tensioned to urge the flange member96 s against the humerus 38 s and compress the bone graft 110 s by apredetermined amount. Thereafter, the coupling device is employed to fixthe ends of the cables relative to one another so as to maintain tensionin the cables 810.

[0114] While the first and second coupling features 812 and 814 havebeen illustrated as being a dovetail member 816 and a dovetail aperture818, respectively, those skilled in the art will appreciate that thefirst and second coupling features 812 and 814 can be constructedsomewhat differently. As illustrated in FIG. 33, for example, the firstcoupling feature 812 t is illustrated as being a pair of pins 830 thatare fixedly coupled to the distal portion 32 t of the stem 12 t and thesecond coupling feature 814 t is illustrated to be a corresponding pairof holes 832 that are formed into the coupling portion 96 t. The pins830 are preferably press-fit or shrunk fit into corresponding holes (notspecifically shown) that are formed into the distal portion 32 t of thestem 12 t but may be secured via other fastening means, such as welding,bonding, or threaded engagement where the pins 830 have a threadedportion that is threadably engaged to the holes in the distal portion 32t. Alternatively, the pins 830 may also be integrally formed as a partof the stem 12 t.

[0115] Another example is illustrated in FIGS. 34 and 35, where thefirst coupling feature 812 u is shown to include a mounting structure840 with an arcuate mounting aperture 842 and the second couplingfeature 814 u is shown to include an attachment hook 846. The mountingstructure 840 is coupled to the distal portion 32 u of the stem 12 u andextends generally perpendicularly outwardly from the base 102 u of theU-shaped portion 40 u. The mounting aperture 842 is generally J-shapedand includes a first portion 850, which is aligned generallyperpendicular to the base 102 u, and an arcuate second portion 852,which extends away, from the stem member 34 u and the base 102 u. Theattachment hook 846 is also generally J-shaped, being configured tomatingly engage the mounting aperture 842. In this regard, theattachment hook 846 includes a leg portion 856 that extends downwardlyfrom the flange member 96u and an arcuate base member 858.

[0116] In coupling the first and second coupling features 812 u and 814u, flange structure 92 u is initially positioned relative to the stem 12u such that the base member 858 is disposed within the first portion 850of the mounting aperture 842. The flange structure 92 u is then rotateddownwardly toward the stem member 34 u to permit the base member 858 toengage the second portion 852 of the mounting aperture 842. The cables810 are thereafter employed to fix the flange structure 92 u relative tothe stem 12 u.

[0117] While the invention has been described in the specification andillustrated in the drawings with reference to a preferred embodiment, itwill be understood by those skilled in the art that various changes maybe made and equivalents may be substituted for elements thereof withoutdeparting from the scope of the invention as defined in the claims. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment illustrated by the drawingsand described in the specification as the best mode presentlycontemplated for carrying out this invention, but that the inventionwill include any embodiments falling within the foregoing descriptionand the appended claims.

What is claimed is:
 1. A prosthetic joint kit comprising: a first stemstructure; a second stem structure; a first bearing component having afirst bearing surface and configured to be releasably coupled to thefirst stem structure; a second bearing component having a second bearingsurface and configured to be releasably coupled to the second stemstructure, the second bearing surface configured to mate with the firstbearing surface; a third bearing component having a third bearingsurface configured to be releasably coupled to the first stem structure;and a fourth bearing component configured to be releasably coupled withthe second stem structure, the fourth bearing component having a fourthbearing surface configured to mate with the third bearing surface;wherein mating of the first and second bearing components together topermit a load to be transmitted between the first and second bearingsurfaces hingedly couples the first and second stem structures together;and wherein the third and fourth bearing components are collectivelyinterchangeable with the first and second bearing components such thatmating of the third and fourth bearing surfaces together permits thefirst and second stem structures to pivot about one another in anunlinked manner.
 2. The prosthetic joint kit of claim 1, wherein each ofthe first and third bearing components includes a pair of slots adaptedto slidingly engage a pair of furcations formed in the first stemstructure.
 3. The prosthetic joint kit of claim 1, further comprising aflange structure for engaging one of the first and second stemstructures, the flange structure being configured to fixate a bone graftand compress the bone graft against the one of the first and second stemstructures.
 4. The prosthetic joint kit of claim 3, wherein the flangestructure is fixedly but releasably engaged to the one of the first andsecond stem structures.
 5. The prosthetic joint kit of claim 4, whereina threaded fastener is employed to fixedly but releasably couple theflange structure to the one of the first and second stem structures. 6.The prosthetic joint kit of claim 4, wherein at least a portion of theflange structure is resiliently biased toward the one of the first andsecond stem structures.
 7. The prosthetic joint kit of claim 1, furthercomprising a tissue fastener for engaging one of the first and secondstem structures, the tissue fastener being adapted to couple a softtissue to the one of the first and second stem structures.
 8. Theprosthetic joint kit of claim 1, further comprising a threaded fastenerfor coupling one of the second and fourth bearing components to thesecond stem.
 9. The prosthetic joint kit of claim 8, wherein each of thesecond and fourth bearing components includes a hook member configuredto engage a mating hook aperture formed in the second stem structure.10. The prosthetic joint kit of claim 8, wherein each of the second andfourth bearing components includes a tray structure for engaging thesecond stem structure.
 11. The prosthetic joint kit of claim 1, whereineach of the second and fourth bearing components includes a stem memberconfigured to engage a mating stem aperture formed in the second stemstructure.
 12. The prosthetic joint kit of claim 11, wherein each of thesecond and fourth bearing components further includes at least one tangconfigured to engage a mating tang aperture formed in the second stemstructure to prevent relative rotation therebetween.
 13. The prostheticjoint kit of claim 1, wherein at least a portion of each of the first,second, third and fourth bearing surfaces is spherical.
 14. Theprosthetic joint kit of claim 1, wherein one of the first and secondstem structures includes a cam structure with a tip, the tip beingconfigured to contact the other one of the first and second stemstructures to limit an amount by which the second stem structure can berotated relative to the first stem structure.
 15. A prosthetic elbow kitcomprising: a first stem structure having a proximal end and a distalend, the proximal end adapted to fit within a medullary canal of ahumerus, the distal end terminating at a pair of furcations; a firstbearing component having a pair of slotted apertures and first andsecond condyle portions, each of the slotted apertures slidinglyengaging one of the pair of furcations, each of the first and secondcondyle portions having a first spherically-shaped bearing portion whichcollectively define a first bearing surface; and a second stem structurehaving a proximal end and a distal end, the distal end of the secondstem structure adapted to fit within an ulna; a second bearing componentcoupled to the proximal end of the second stem structure, the secondbearing component including a pair of second spherically-shaped bearingportions that collectively define a second bearing surface configured tomate with the first bearing surface.
 16. The prosthetic elbow kit ofclaim 15, wherein the first bearing component further includes a pinportion, the pin portion intersecting each of the firstspherically-shaped bearing portion and coupling the first and secondcondyle portions together.
 17. The prosthetic elbow kit of claim 16,wherein the first bearing component is unitarily formed.
 18. Theprosthetic elbow kit of claim 16, wherein at least one of the first andsecond condyle portions includes a pin aperture sized to receive the pinportion.
 19. The prosthetic elbow kit of claim 16, wherein the secondbearing component includes a through hole sized to receive the pinportion.
 20. The prosthetic elbow kit of claim 16, wherein each of thefirst and second condyle portions is formed from a material selectedfrom a group of materials consisting of polyethylene, cobalt chromiumalloy, stainless steel, pyrolytic carbon and ceramics.
 21. Theprosthetic elbow kit of claim 15, further comprising a flange structurefor releasably engaging one of the first and second stem structures, theflange structure being configured to fixate a bone graft and compressthe bone graft against the one of the first and second stem structures.22. The prosthetic elbow kit of claim 21, wherein the flange structureis fixedly but releasably engaged to the one of the first and secondstem structures.
 23. The prosthetic elbow kit of claim 22, wherein athreaded fastener is employed to fixedly but releasably couple theflange structure to the one of the first and second stem structures. 24.The prosthetic elbow kit of claim 21, wherein at least a portion of theflange structure is resiliently biased toward the one of the first andsecond stem structures.
 25. The prosthetic elbow kit of claim 15,further comprising a tissue fastener for engaging one of the first andsecond stem structures, the tissue fastener being adapted to couple asoft tissue to the one of the first and second stem structures.
 26. Theprosthetic elbow kit of claim 15, wherein the first and second stemstructures are hingedly coupled together when the first and secondbearing surfaces are mated together.
 27. The prosthetic elbow kit ofclaim 26, wherein the second bearing component is fixedly coupled to thesecond stem structure.
 28. The prosthetic elbow kit of claim 26, furthercomprising a third bearing component which is interchangeable with thesecond bearing component, the third bearing component having a lateralbuttress adapted for receiving a capitellum of the humerus.
 29. Theprosthetic elbow kit of claim 28, further comprising a third stem andthird and fourth bearing components, the third stem having a proximalend and a distal end, the distal end of the third stem adapted to fitwithin a medullary canal of a radius, the third bearing componentcoupled to the proximal end of the third stem and defining a thirdbearing surface, the fourth bearing component being interchangeable withthe first bearing component, the fourth bearing component having a pairof slotted apertures, first and second condyle portions and a lateralextension, each of the slotted apertures slidingly engaging one of thepair of furcations, each of the first and second condyle portions havinga first spherically-shaped bearing portion which collectively define afirst bearing surface, the lateral extension adapted to replace at leasta portion of a capitellum of the humerus, the lateral extension defininga fourth bearing surface configured to mate with the third bearingsurface.
 30. The prosthetic elbow kit of claim 29, wherein at least aportion of each of the third and fourth bearing surfaces is sphericallyshaped.
 31. The prosthetic elbow kit of claim 15, wherein the firstbearing surface supports the second bearing surface for pivotal movementthereon in an unlinked manner whereby the first and second stemstructures are not hingedly coupled.
 32. The prosthetic elbow kit ofclaim 15, wherein the second stem structure is a threaded fastener. 33.The elbow kit of claim 15, wherein one of the first and second stemstructures includes a cam structure with a tip, the tip being configuredto contact the other one of the first and second stem structures tolimit an amount by which the second stem structure can be rotatedrelative to the first stem structure.
 34. A prosthetic joint kitcomprising: a first stem structure having a first portion that isadapted to fit within a medullary canal of a first bone; a first bearingcomponent coupled to the first stem, the first bearing component havingfirst and second condyle portions, each of the first and second condyleportions being at least partially spherically shaped; a second stemstructure having a second portion that is adapted to fit within amedullary canal of a second bone; a second bearing component coupled tothe second stem structure and having a second bearing surface configuredto engage the first and second condyle portions, the second bearingsurface being defined by a first characteristic constraint; and a thirdbearing component interchangeable with the second bearing component, thethird bearing component having a third bearing surface configured toengage the first and second condyle portions, the third bearing surfacebeing defined by a second constraint characteristic.
 35. The prostheticjoint kit of claim 34, wherein each of the second and third bearingsurfaces is formed by a plurality of surface portions, each of thesurface portions having a predetermined constraint angle.
 36. Theprosthetic joint kit of claim 35, wherein a first surface portion of thesecond bearing surface has a predetermined first constraint angle whichis smaller than a predetermined second constraint angle of a firstsurface portion of the third bearing surface.
 37. The prosthetic jointkit of claim 34, wherein a bearing aperture is formed in a second end ofthe second stem structure, the bearing aperture including a groove forreceiving a retaining ring, the retaining ring operatively engaging thesecond end of the second stem structure and one of the second and thirdbearing components to fixedly but releasably couple the second stemstructure and the one of the second and third bearing componentstogether.
 38. The prosthetic joint kit of claim 37, wherein each of thesecond and third bearing components includes at least one tab forengaging a tab recess in the bearing aperture, the tab and the tabrecess cooperating to prevent relative rotation between the second stemstructure and the one of the second and third bearing components. 39.The prosthetic joint kit of claim 34, wherein a bearing aperture isformed in a second end of the second stem structure, the bearingaperture including a hook member, the second and third bearingcomponents including a clip member adapted to releasably engage the hookmember.
 40. The prosthetic joint kit of claim 39, wherein each of thesecond and third bearing components further includes a molded portion,the clip member being formed from metal and molded into the moldedportion.
 41. A prosthetic joint kit comprising: a first stem structurehaving a first end adapted to fit within a medullary canal of a firstbone; a first bearing component coupled to the first stem, the firstbearing component having first and second condyle portions, each of thefirst and second condyle portions being at least partially sphericallyshaped; a second stem structure having a second end that is adapted tofit within a medullary canal of a second bone; and a second bearingcomponent coupled to the second stem structure and having a secondbearing surface with a first bearing portion that is configured toengage the first condyle portion and a second bearing portion that isconfigured to engage the second condyle portion, each of the first andsecond bearing portions having a first spherical portion and a secondspherical portion, the first spherical portion being formed along afirst axis, the second spherical portion being formed along a secondaxis, the second axis being skewed to the first axis in at least oneorthogonal direction.
 42. The prosthetic joint kit of claim 41, whereinthe first spherical portion of the first bearing portion is defined by afirst centerpoint and a predetermined bearing surface radius, the secondspherical portion of the first bearing portion is defined by a secondcenterpoint and the predetermined bearing surface radius, the firstspherical portion of the second bearing portion is defined by a thirdcenterpoint and the predetermined bearing surface radius, the first andthird centerpoints being spaced apart by a predetermined spacingdistance, the second and third centerpoints being spaced apart by thepredetermined spacing distance, the first, third and second centerpointscooperating to define a predetermined constraint angle.
 43. Theprosthetic joint kit of claim 42, further comprising a third bearingcomponent having a third bearing surface with a third bearing portionthat is configured to engage the first condyle portion and a fourthbearing portion that is configured to engage the second condyle portion,each of the third and fourth bearing portions having a third sphericalportion and a fourth spherical portion, the third spherical portionbeing formed along a third axis, the fourth spherical portion beingformed along a fourth axis, the fourth axis being skewed to the thirdaxis in a manner that is differs from that manner in which the secondaxis is skewed to the first axis, and wherein the second and thirdbearing components are selectively and alternatively coupled to thefirst bearing component.
 44. The prosthetic joint kit of claim 43,wherein the first and second axes are contained in a single plane. 45.The prosthetic joint kit of claim 44, wherein the third axis iscontained in a plane that intersects a plane in which the fourth axis iscontained.
 46. The prosthetic joint kit of claim 43, wherein the firstaxis is contained in a first plane that intersects a second plane inwhich the second axis is contained and the third axis is contained in athird plane that intersects a fourth plane in which the fourth axis iscontained, the first and second planes being skewed relative to oneanother by a first angle and the third and fourth planes being skewedrelative to one another by a second angle.
 47. The prosthetic joint kitof claim 46, wherein the first and second angles are different.
 48. Theprosthetic joint kit of claim 43, wherein the second and third bearingcomponents are selectively and alternatively coupled to the second stemstructure.
 49. The prosthetic joint kit of claim 43, wherein the thirdspherical portion of the third bearing portion is defined by a fourthcenterpoint and the predetermined bearing surface radius, the fourthspherical portion of the third bearing portion is defined by a fifthcenterpoint and the predetermined bearing surface radius, the thirdspherical portion of the fourth bearing portion is defined by a sixthcenterpoint and the predetermined bearing surface radius, the fourth andsixth centerpoints being spaced apart by the predetermined spacingdistance, the fifth and sixth centerpoints being spaced apart by thepredetermined spacing distance, the fourth, sixth and fifth centerpointscooperating to define a predetermined second constraint angle having amagnitude that is different than a magnitude of the constraint anglethat is defined by the first, third and second centerpoints.
 50. Theprosthetic joint kit of claim 41, wherein the second bearing portion isa mirror image of the first bearing portion.
 51. The prosthetic jointkit of claim 41, wherein a transition zone is formed between the firstand second spherical portions on at least one of the first and secondbearing portions.
 52. A prosthetic joint kit comprising: a first stemstructure having a first end adapted to fit within a medullary canal ofa first bone; a first bearing component coupled to the first stem, thefirst bearing component having first and second condyle portions, eachof the first and second condyle portions being at least partiallyspherically shaped; a second stem structure having a second end that isadapted to fit within a medullary canal of a second bone; and aplurality of second bearing components, each of the second bearingcomponents being configured to be interchangeably coupled to the secondstem structure, each of the second bearing components having a secondbearing surface that is configured to engage the first and secondcondyle portions, each of the second bearing surfaces being configureddifferently from the bearing surfaces of a remaining quantity of thesecond bearing components, each of the second bearing surfaces providinga varying degree of constraint between the first and second stemstructures as the first and second stem structures are rotated relativeto one another.
 53. The prosthetic joint kit of claim 52, wherein atleast one of the bearing surfaces is configured such that the varyingdegree of constraint is provided in a direction that is coincident to anaxis about which the first and second stem structures rotate relative toone another.
 54. The prosthetic joint kit of claim 52, wherein at leastone of the bearing surfaces is configured such that the varying degreeof constraint is provided in a varus/valgus direction.
 55. Theprosthetic joint kit of claim 52, wherein at least one of the bearingsurfaces is configured such that the varying degree of constraint isprovided in both a direction that is coincident to an axis about whichthe first and second stem structures rotate relative to one another andin a varus/valgus direction.
 56. The prosthetic joint kit of claim 52,further comprising a third bearing component that is configured to besubstituted for the second bearing components and selectively coupled tothe second stem structure, the third bearing component having a thirdbearing surface that is configured to engage the first and secondcondyle portions, the third bearing surface being configured so as toprovide a constant degree of constraint between the first and secondstem structures as the first and second stem structures are rotatedrelative to one another.
 57. A prosthetic joint comprising a first stemstructure and a flange structure, the first stem structure having an endadapted to engage a first bone, the flange structure being releasablycoupled to the first stem structure, the flange structure beingconfigured to transmit a compressive force to a bone graft locatedproximate the flange structure to fixate and compress the bone graft.58. The prosthetic joint of claim 57, wherein the flange structureincludes a flange member and a hollow tapered mounting member, themounting member engaging a tapered portion of a hole formed in the firststem structure.
 59. The prosthetic joint of claim 58, further comprisinga threaded fastener extending through the mounting member and threadablyengaging a threaded portion of the hole.
 60. The prosthetic joint ofclaim 57, wherein at least one cable is employed to fixedly butreleasably couple the flange structure to the first stem structure. 61.The prosthetic joint of claim 60, wherein a pair of mating couplingfeatures are employed to position the flange structure relative to thefirst stem structure.
 62. The prosthetic joint of claim 61, wherein thepair of mating coupling features includes at least one coupling membercoupled to one of the flange structure and the first stem structure andat least one coupling aperture formed into the other one of the flangestructure and the first stem structure and being sized to receive the atleast one coupling member.
 63. The prosthetic joint of claim 62, whereinthe at least one coupling member includes a cylindrically shaped pin andthe at least one coupling aperture includes a cylindrically shaped hole.64. The prosthetic joint of claim 62, wherein the coupling member has atrapezoidal cross-section.
 65. The prosthetic joint of claim 62, whereinthe flange structure includes at least one aperture for receiving the atleast one cable.
 66. The prosthetic joint of claim 65, wherein the atleast one aperture is a plurality of cross-holes formed through theflange structure.
 67. The prosthetic joint of claim 66, wherein each ofthe cross-holes is formed along an axis that is generally perpendicularto a longitudinal axis of the flange structure.
 68. A prosthetic jointcomprising a first stem structure and a flange structure, the first stemstructure having an end that is adapted to engage a medullary canal of afirst bone, the flange structure being coupled to the first stemstructure and resiliently biased toward the first stem structure, theflange structure being configured to transmit a compressive force to abone graft located between the first stem structure and the flangestructure.
 69. The prosthetic joint of claim 68, wherein the flangestructure includes an arcuately shaped flange member.
 70. The prostheticjoint of claim 60, wherein the flange structure is fixedly butreleasably engaged to the first stem structure.
 71. The prosthetic jointof claim 70, wherein a threaded fastener is employed to fixedly butreleasably couple the flange structure to the first stem structure. 72.The prosthetic joint of claim 70, wherein at least one cable is employedto fixedly but releasably couple the flange structure to the stemstructure.
 73. The prosthetic joint of claim 72, wherein a pair ofmating coupling features are employed to position the flange structurerelative to the first stem structure.
 74. The prosthetic joint of claim73, wherein the pair of mating coupling features includes at least onecoupling member coupled to one of the flange structure and the firststem structure and at least one coupling aperture formed into the otherone of the flange structure and the first stem structure and being sizedto receive the at least one coupling member.
 75. The prosthetic joint ofclaim 74, wherein the at least one coupling member includes acylindrically shaped pin and the at least one coupling aperture includesa cylindrically shaped hole.
 76. The prosthetic joint of claim 74,wherein the coupling member has a trapezoidal cross-section.
 77. Theprosthetic joint of claim 74, wherein the flange structure includes atleast one aperture for receiving the at least one cable.
 78. Theprosthetic joint of claim 77, wherein the at least one aperture is aplurality of cross-holes formed through the flange structure.
 79. Theprosthetic joint of claim 78, wherein each of the cross-holes is formedalong an axis that is generally perpendicular to a longitudinal axis ofthe flange structure.
 80. A linked prosthetic joint comprising: a firststem structure; a second stem structure; a first bearing coupled to thefirst stem structure; a second bearing coupled to the second stemstructure and including a slotted aperture; and a coupling structure forcoupling the first and second bearings, the coupling structure includinga coupling member that is fixedly coupled to the first bearing, thecoupling member being received by the slotted aperture; wherein thefirst and second bearing components are mated together to permit a loadassociated with the operation of the linked prosthetic joint to betransmitted therebetween and wherein the load is not transmitted throughthe coupling member.
 81. The linked prosthetic joint of claim 80,wherein the coupling structure further includes a stop member that isfixedly coupled to an end of the coupling member, the stop member beingconfigured with a width dimension that is larger than a width dimensionof the coupling member.
 82. The linked prosthetic joint of claim 81,wherein the slotted aperture includes a first portion and a secondportion, the first portion being sized larger than the width dimensionof the stop member and the second portion being sized larger than thewidth dimension of the coupling member and smaller than the widthdimension of the stop member.
 83. The linked prosthetic joint of claim81, wherein the stop member is generally cylindrically shaped and thecoupling member is coupled to the stop member along an axis that isgenerally perpendicular to a longitudinal axis of the stop member. 84.The linked prosthetic joint of claim 83, wherein the portion of theslotted aperture in which the stop member rotates is generallyspherically shaped.
 85. The linked prosthetic joint of claim 80, whereinthe second bearing includes a spherically shaped bearing surface. 86.The linked prosthetic joint of claim 80, wherein the second stemstructure and the second bearing are a one piece fabrication.
 87. Thelinked prosthetic joint of claim 80, wherein the first stem structureand the first bearing are a one piece fabrication.
 88. The linkedprosthetic joint of claim 87, wherein the one piece fabrication includesthe first stem structure, the first bearing and the coupling structure.89. A linked prosthetic joint comprising: a first stem structure; afirst bearing coupled to the first stem structure, the first bearinghaving a concave bearing surface; a second stem structure; a secondbearing coupled to the second stem structure, the second bearingincluding a convex bearing surface that is configured to matingly engagethe concave bearing surface; a slotted aperture formed into one of thefirst and second bearings; and a coupling structure for coupling thefirst and second bearings, the coupling structure including a couplingmember that is fixedly coupled to the other one of the first and secondbearings and, the coupling member being received by the slottedaperture; wherein the first and second bearing components are matedtogether to permit a load associated with the operation of the linkedprosthetic joint to be transmitted therebetween and wherein the load isnot transmitted through the coupling member.
 90. The linked prostheticjoint of claim 89, wherein the coupling structure further includes astop member that is fixedly coupled to an end of the coupling member,the stop member being configured with a width dimension that is largerthan a width dimension of the coupling member.
 91. The linked prostheticjoint of claim 90, wherein the slotted aperture includes a first portionand a second portion, the first portion being sized larger than thewidth dimension of the stop member and the second portion being sizedlarger than the width dimension of the coupling member and smaller thanthe width dimension of the stop member.
 92. The linked prosthetic jointof claim 91, wherein the stop member is generally cylindrically shapedand the coupling member is coupled to the stop member along an axis thatis generally perpendicular to a longitudinal axis of the stop member.93. The linked prosthetic joint of claim 92, wherein the portion of theslotted aperture in which the stop member rotates is generallyspherically shaped.
 94. The linked prosthetic joint of claim 89, whereinthe second stem structure and the second bearing are a one piecefabrication.
 95. The linked prosthetic joint of claim 89, wherein thefirst stem structure and the first bearing are a one piece fabrication.